P2X receptors (P2XRs) constitute the most recently cloned superfamily of ligand-gated ion channels LGICs). P2XRs are fast acting, cation-permeable ion channels that are gated by synaptically released extracellular adenosine 5'-triphosphate (ATP) and are widely distributed in the CNS. Studies to date by our lab and others show that: 1) P2XRs mediate behaviors that are affected by ethanol;2) P2XRs modulate activity in receptors systems believed to be targets mediating ethanol-induced behaviors;3) Ethanol inhibits ATP-activated current in hippocampal and nucleus accumbens neurons;4) Ethanol inhibits ATP-activation in wildtype P2XRs expressed in Xenopus oocytes and HEK 293 cells and 5) Sensitivity to ethanol of P2XRs is subunit dependent. These findings are consistent with the notion that ethanol-induced changes in P2XR function may directly or indirectly play a role in causing or modulating some ethanol behavioral effects. Definitive evidence must await development of selective P2XR antagonists and sufficient knowledge regarding the actions and molecular targets of ethanol in P2XRs. The current proposal addresses the latter by beginning to answer three key questions: 1) What recombinant P2XR subtypes are sensitive to ethanol? 2) What native P2XR subtypes are sensitive to ethanol? This will require comparing the pharmacological and electrophysiological characteristics of ethanol sensitive recombinant receptors expressed in Xenopus oocytes and HEK293 cells and native P2XRs in hippocampal and nucleus accumbens neurons and 3) What are the molecular sites/mechanisms of ethanol action in P2XRs? The proposed work likely will contribute foundation information that will lead to initial molecular models of sites of action for ethanol in P2XRs and will set the stage for future investigations that will use this knowledge to develop knock in and null mutant ("knock out") mice that can be used to test the roles that specific P2XRs play in mediating physiological and behavioral effects of ethanol.